It has long been known that compounds of silver exhibit antibacterial property. For instance, calcium carbonate to which silver is added has been extensively used for the sterilization of the dechlorinated tap water.
It has also been known that antibacterial property is exhibited by a polymer that contains silver acrylate and/or silver methacrylate as a structural unit. Japanese Patent Publication No. 43123/1983 discloses an antibacterial semi-permeable composed of the above polymer and a cellulose ester.
Furthermore, Japanese Laid-Open Patent Publication No. 154746/1988 discloses an antibacterial film composed of a synthetic resin which contains dispersed therein a hygroscopic agent and zeolite-type solid particles that hold metal ions such as silver ions that exhibit antibacterial action by the exchange of ions, the zeolite-type solid particles having a specific surface area of greater than 150 m.sup.2 /g and an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio of smaller than 14.
According to the method of producing the antibacterial polymer of the former publication, the silver acrylate and/or the silver methacylate is polymerized, or silver nitrate is reacted with polyacrylic acid, polymethacrylic acid or a copolymer thereof. However, the antibacterial polymer that is obtained lacks thermal stability under dry heated conditions, and does not apparently lend itself for such applications as forming films by the heat treatment or forming containers through the heat-molding.
According to the method of blending the silver ion-exchanged zeolite in the resin disclosed in the latter publication, there remain problems in regard to producing the silver ion-exchanged zeolite and in regard to that the sterilizing power decreases if there exist silver oxides in the zeolite, though there is problem with regard to heat resistance. There still exists a problem in that the silver ion-exchanged zeolite is alkaline just as the zeolite is in general, and hence tends to hydrolyze the resin that is blended.